1. Field of the Invention
The present invention relates to scroll compressors and, more particularly, to a scroll compressor provided with a scroll wrap designed at a predetermined section to be different from the other sections in thickness, thus being improved in its gas refrigerant compression efficiency.
2. Description of the Prior Art
FIG. 1 is a sectional view of a conventional scroll compressor. FIG. 2 is a plan sectional view, showing the profile of the wraps of the fixed and orbiting scrolls of a conventional symmetric scroll compressor.
As shown in the drawings, the conventional symmetric scroll compressor has a main frame 20 and a sub-frame 25, which are set within a hermetic casing 1 at upper and lower positions. In such a conventional symmetric scroll compressor, a compression part 10, used for compressing gas refrigerant prior to discharging the compressed gas refrigerant, is set on the main frame 20 within the casing 1. A motor 30 is set within the space defined between the main frame 20 and the sub-frame 25, and is used for driving the compression part 10.
The above motor 30 comprises a stator 31 and a rotor 33, while the compression part 10 comprises a fixed scroll 11 and a orbiting scroll 15. The fixed and orbiting scrolls 11 and 15 have involute wraps 11a and 15a, with a phase difference of 180xc2x0 formed between the two wraps 11a and 15a, The two wraps 11a and 15a of the scrolls 11 and 15 engage with each other to form variable compression chambers C and Cxe2x80x2 between them.
When the stator 31 of the motor 30 is turned on, the rotor 33 is rotated along with the motor shaft 35, and so the orbiting scroll 15 is orbited relative to the fixed scroll 11.
When the orbiting scroll 15 is orbited relative to the fixed scroll 11 as described above, the variable compression chambers C and Cxe2x80x2 formed between the two wraps 11a and 15a of the scrolls 11 and 15 are gradually reduced in their volumes and are increased in their pressures in a direction toward the center of the compression part 10. Therefore, it is possible to compress the gas refrigerant introduced into the compression part 10 through an inlet port 16 and to discharge the compressed gas refrigerant from the compression part 10 into a refrigerant discharging pipe through an outlet port 19. Such a gas refrigerant compressing process of the conventional symmetric scroll compressor is shown in FIG. 4 in detail.
In order to minimize a loss during the gas refrigerant compressing process, it is necessary to prevent a leakage of compressed gas refrigerant. In the conventional symmetric scroll compressor, the compressed gas refrigerant may leak in a radial direction through axial gaps and leak in a tangential direction through radial gaps.
Such a tangential leakage of compressed gas refrigerant through radial gaps is caused by the gaps formed between the two wraps 11a and 15a at a plurality of tangential contact points P of the two scrolls 11 and 15.
FIG. 3 is a view, showing the design factors of a conventionally designed scroll of the conventional symmetric scroll compressor.
As shown in the drawing, the wrap 11a or 15a of each of the fixed and orbiting scrolls 11 and 15 of the conventional symmetric scroll compressor is shaped as an involute curve, comprising an inside involute and an outside involute designed to have a phase difference of xc2x1xcex1 between them. Each of the wraps 11a and 15a also has a constant thickness T.
That is, the thickness T of each wrap 11a or 15a is expressed as follows: T=L0xe2x88x92Li=a (xcex8+xcex1)xe2x88x92a (xcex8xe2x88x92xcex1)=2axcex1. This means that each wrap 11a or 15a has a constant thickness T from the first to the last.
However, such a conventional symmetric scroll compressor is problematic due to the constant thickness of the wraps 11a and 15a, That is, since the wraps 11a and 15a of the fixed and orbiting scrolls 11 and 15 of the conventional symmetric scroll compressor have such a constant thickness T as described above, a plurality of gaps are undesirably formed between the two wraps 11a and 15a at the tangential contact points P of the two scrolls 11 and 15 as shown in FIG. 2 due to a requirement of machining allowance and/or assembling allowance of the two wraps 11a and 15a. In addition, the size of such gaps is not uniform, and so the amounts of leaking gas refrigerant from the compression chambers C and Cxe2x80x2 of the compression part 10 are different from each other. This finally causes a reduction in the gas refrigerant compression efficiency and an increase in operational noises of such a conventional symmetric scroll compressor.
If the profile of each wrap 11a or 15a of the two scrolls 11 and 15 is shaped as an ideal involute curve, it is possible to allow the tangential contact points P of the two scroll wraps 11a and 15a to be completely free from such undesired gaps or to have only negligible gaps. In such a case, the symmetric scroll compressor accomplishes desired gas refrigerant compression efficiency. However, it is practically impossible to form such an ideal involute curve in the scroll wraps 11a and 15a due to a requirement of machining allowance and/or assembling allowance of the two wraps 11a and 15a, Therefore, a plurality of gaps having different sizes are formed at the tangential contact points P of the two scroll wraps 11a and 15a, thereby undesirably allowing a leakage of compressed gas refrigerant. This results in a reduction in the gas refrigerant compression efficiency and an increase in operational noises of the conventional symmetric scroll compressors.
FIG. 5 is a plan sectional view, showing the profile of the wraps of the fixed and orbiting scrolls of a conventional asymmetric scroll compressor.
As shown in the drawings, the conventional asymmetric scroll compressor is designed such that the involute terminal angle xcfx86exe2x80x2 of the fixed scroll wrap 15xe2x80x2 is larger than the involute terminal angle xcfx86e of the orbiting scroll wrap 11xe2x80x2 at an angle of 180xc2x0, with a plurality of variable compression chambers formed between the two scroll wraps 11xe2x80x2 and 15xe2x80x2. This asymmetric scroll compressor is preferably increased in the volume of its sucked gas refrigerant by at least 10% in comparison with the conventional symmetric scroll compressor without changing the inner diameters of the main and sub-frames.
In such scroll compressors, the term xe2x80x9cinvolute terminal angle of a scroll wrapxe2x80x9d means an angle formed between the initial end and the terminal end of the scroll wrap.
Different from the conventional symmetric scroll compressor, the conventional asymmetric scroll compressor has only one gas refrigerant suction part, and so the asymmetric scroll compressor does not have any gas refrigerant suction passage formed around the outer edge of the orbiting scroll. Therefore, this asymmetric scroll compressor is less likely to overheat the sucked gas refrigerant, and is improved in its volume efficiency in comparison with the symmetric scroll compressor. The asymmetric scroll compressor is thus allowed to gradually and smoothly suck gas refrigerant into its compression part, and is remarkably reduced in its pulse vibration in comparison with the symmetric scroll compressor when the compressed air refrigerant is discharged from the compressor.
However, the conventional asymmetric scroll compressor is problematic as follows. That is, the asymmetric scroll compressor uses the extended inside involute section xcfx86excx9cxcfx86exe2x80x2 of the fixed scroll wrap 11xe2x80x2 as a compression chamber different from the conventional symmetric scroll compressor which does not use such an inside involute section xcfx86excx9cxcfx86exe2x80x2 as the compression chamber. In addition, the fixed and orbiting scrolls of the asymmetric scroll compressor are designed such that the involute terminal angle xcfx86exe2x80x2 of the fixed scroll wrap 15xe2x80x2 is larger than that of the orbiting scroll wrap 11xe2x80x2 at an angle of 180xc2x0 different from the conventional symmetric scroll compressor. Therefore, the number of gaps allowing a leakage of compressed gas refrigerant is undesirably increased in the asymmetric scroll compressor.
FIG. 6 is a view, showing the profile of a scroll wrap of the conventional asymmetric scroll compressor having a dimensional error caused by both machining allowance and assembling allowance. When the orbiting scroll wrap 11xe2x80x2 is not shaped as an ideal involute curve, but has a dimensional error due to the machining allowance and the assembling allowance as shown in FIG. 6, it is fortunately possible to prevent a leakage of compressed gas refrigerant at the outermost contact point xcex40 (see FIG. 7) having a low pressure difference since the fixed scroll wrap 11xe2x80x2 comes into close contact with the orbiting scroll wrap 15xe2x80x2. However, it is almost impossible to prevent a formation of gaps at the inside contact points xcex41 and xcex42 (see FIG. 7), and so compressed gas refrigerant undesirably leaks through the gaps at the inside contact points xcex41 and xcex42. Since the pressure difference at the inside contact points xcex41 and xcex42 is so high that the leakage of the compressed gas refrigerant at said points xcex41 and xcex42 seriously influences the compression efficiency of the compressor, the asymmetric scroll compressor is undesirably reduced in its compression efficiency.
In addition, such a conventional asymmetric scroll compressor is designed such that the sealing structure of the compressor for preventing a radial leakage of compressed gas refrigerant is formed by biasing the orbiting scroll wrap 15xe2x80x2 toward the fixed scroll wrap 11xe2x80x2. However, this structure undesirably causes imbalance at the contact points xcex40, xcex41 and xcex42 due to dimensional error caused by the machining allowance and the assembling allowance, thus finally impacting the two scroll wraps 11xe2x80x2 and 15xe2x80x2 at the contact points between them and generating operational noises of the compressor.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a scroll compressor, of which at least one of fixed and orbiting scroll wraps is formed at a predetermined section thereof to be different from the other sections in thickness, and which is thus improved in its gas refrigerant compression efficiency and is reduced in its operational noises.
In order to accomplish the above object, the present invention provides a scroll compressor, comprising fixed and orbiting scrolls having involute wraps, the involute fixed and orbiting scroll wraps engaging with each other to form a plurality of variable compression chambers between them, wherein at least one of the involute fixed and orbiting scroll wraps is formed at a predetermined section thereof to be thicker than the other sections.
In an embodiment, the present invention provides a scroll compressor, comprising fixed and orbiting scrolls having involute wraps, the involute fixed and orbiting scroll wraps engaging with each other to form a plurality of variable compression chambers between them, wherein at least one of the involute fixed and orbiting scroll wraps is formed at a middle section thereof to be thicker than a terminal section.
In the above scroll compressor, the middle section of at least one of the involute fixed and orbiting scroll wraps extends from a point having an angle of xcfx86e-4xcfx80 to another point having an angle of xcfx86e-2xcfx80, with the involute terminal angle of the wrap formed from the initial end to the terminal end of the wrap being designated by xcfx86e.
In another embodiment, the present invention provides an asymmetric scroll compressor, comprising fixed and orbiting scrolls having involute wraps, with the involute terminal angle xcfx86exe2x80x2 of the fixed scroll wrap being larger than the involute terminal angle xcfx86e of the orbiting scroll wrap by a predetermined angle, thus forming an extension part xcfx86excx9cxcfx86exe2x80x2, wherein the involute fixed scroll wrap is offset at the inside surface of the extension part by a predetermined thickness, thus forming a gap between the fixed and orbiting scroll wraps at the extension part.
In a further embodiment, the present invention provides an asymmetric scroll compressor, comprising fixed and orbiting scrolls having involute wraps, with the involute terminal angle xcfx86exe2x80x2 of the fixed scroll wrap being larger than the involute terminal angle xcfx86e of the orbiting scroll wrap by a predetermined angle, thus forming an extension part xcfx86excx9cxcfx86exe2x80x2, wherein the orbiting scroll wrap is offset at its outside surface at a portion corresponding to the extension part of the fixed scroll wrap by a predetermined thickness, thus forming a gap between the fixed and orbiting scroll wraps at the extension part.